As a relatively simple miniature generator heretofore used as a power source of a toy, etc., a cordless audio reproducing (Japanese Laying-open Publication No. 52-27407 of a patent application) is known.
In the prior art cordless audio reproducing apparatus, a worm shaft is coupled to a rotary shaft of a generator. Bearing members directly supporting opposite ends of the rotary shaft are formed in a unitary body with a case by casting. This means that the bearing members are made from the same material as that of the case. Therefore, the bearing members are worn out in a short time and cause a vibration.
Further, it is difficult to establish proper alignment between the center of the rotary shaft and the center of a yoke assembly in the building process of the apparatus. Additionally, the prior art apparatus is subject to large changes in the generated voltage with revolution speed of the rotary shaft.